He is 'seeking revenge for' his father's murder. [=he wants to harm the person who killed his father]
He swore to 'take (his) revenge on' his enemies. [=to harm his enemies]
The bombing was 'in revenge for' the assassination of their leader.
(..) But here in Meereen, I cannot pursue my talents. I've ordered the Second Sons to patrol the streets to stop the revenge killing. You've ordered us to be night watchmen. And as for women, there are thousands in Meereen you can pursue. (..)2014 TvShow: Game of Thrones Title: Mockingbird Season: 4 Episode 7